As explained in § 7.2 and 8.3§
observations of more than ks
duration are typically split up in smaller observing intervals; the number of
such intervals is arbitrary and it is impossible to predict in general
into how many intervals an observation of some given length will be
subdivided. Some specific types of observations may lose their scientific
usefulness if split up into too many subintervals. The contiguous
observation constraint allows
the guest investigator to specify the maximum number of data intervals
(in the ``Maximum Number of Data Intervals'' entry)
and hence to prevent his observations from being split up into too many
observing intervals. The requested observing time will then be allocated
in no more than the specified number of observing intervals.
Guest investigators wishing to have contiguous data should carefully
consider the maximum possible number of data intervals. The number
of viewing opportunities with lengths in excess of 3 ks is quite small
and therefore insisting on too many long observing intervals can make
a requested observation unschedulable.